Changes in proteoglycans and collagen will be studied in the growth cartilages of costochondral junctions. Attempts will also be made to examine these components in metaphyseal bone which has a large component of calcified cartilage. In order to get a dynamic view of changes in the matrix, studies will be performed in vivo using 35 S-sulfate and in vitro using radioactive proline. The turnover of these precursors in proteoglycans and collagen will be assessed on a zonal basis as a function of time as endochondral growth proceeds. The biosynthetic potential of the different zones will be assessed. Soluble, resistant, aggregated and unaggregated proteoglycans will be studied as well as the solubilities and types of collagen found in the zones. In addition, a possible complex of collagen and proteoglycans will be looked for in bone as this might constitute a calcifiable substrate.